The present invention relates to a method for recording and analyzing pain diagrams in which a patient or physician draws on a body image the location of pain suffered by the patient. Pain diagrams have been used for many years but are normally used merely for quick visual review to identify anatomic locations of pain.
Pain diagrams are routinely used in pain specialist offices and in clinical trials of pain therapy. Previous attempts to automate analysis of pain diagrams have been of limited value and have not provided detailed quantitative evaluation or been applicable to all of the many body image designs used in medical practice.
North et al (“Automated ‘pain drawing’ analysis by computer-controlled, patient-interactive neurological stimulation system”, Pain. 1992 July; 50:51-7 and “Patient-interactive, computer-controlled neurological stimulation system: clinical efficacy in spinal cord stimulator adjustment, J Neurosurg. 1992 June; 76:967-72; also see U.S. Pat. No. 6,654,642) have used computer technology for direct recording by the patient of pain shapes. Using a pointing device and computer screen display, a patient with neurostimulation implants draws anatomic locations where pain is felt on a computerized body outline. The computer system adjusts the amount of electric pulse stimulation of the nerve so as to optimize pain relief. However, it does not provide diagnostic information or analysis of the paper pain diagrams used in ordinary clinical practice.
Other workers have divided the body image into a series of rectangles using a transparent grid; an observer then manually records which rectangles represent painful areas. These data may then be coded to computer files for analysis or analyzed manually. Using a grid system, larger areas of pain measured have been correlated with greater disease severity and poorer response to treatment. Thus, Toomingas (“Characteristics of pain drawings in the neck-shoulder region among the working population”, Int Arch Occup Environ Health. 1999 March; 72(2):98-106) used an 878 pixel transparent grid to classify pain location in the neck-shoulder area. Total pain area, left-right distribution and symmetry were correlated with symptom chronicity and severity of disease. Takata and Hirotani (“Pain drawing in the evaluation of low back pain”, Int Orthop. 1995; 19(6):361-6) used a grid system to show that patients with larger numbers of leg grid rectangles involved in pain showed poorer treatment outcomes. Similarly, Toomey et al (“Relationship of pain drawing scores to ratings of pain description and function”, Clin J. Pain. 1991 December; 7:269-74) found that larger pain areas were related to increased disability in patients with chronic pain.
Digital subtraction is an established computer technique used in clinical medicine, e.g., for magnetic resonance visualization of blood vessels. It involves computer comparisons of pairs of pixels across two images. Normally, a baseline image is obtained prior to some intervention such as injection of a radio-opaque material into a blood vessel and compared with an image obtained after the injection. The idea of digital subtraction dates back to the 1930s, when the Dutch radiologist des Plantes produced subtraction images of contrast-filled vessels using plain film. From the “mask” image (i.e. the image of the object just before the contrast medium is injected) he produced a positive copy, onto which the images with contrast medium were overlaid to coincide, thus producing a subtraction image only displaying the contrast-filled vessels. Digital subtraction has not previously been used in analysis of pain diagrams.
The computer generation of composite images is an established technique used in medicine. For example, composite images are useful in integrating the data from multiple frames from a magnetic resonance image of the brain, using the techniques of coregistration (where images are superimposed on each other) followed by display on a composite image of the average intensity on a gray or color scale. Composite images have not been hitherto used for analysis of pain diagrams.
A further established computer technique, used in cartography, allows the user to “drill” up and down through different levels of detail in, for example, a map of the world. Thus, Internet sites such as mapquest.com allow the user to specify an address, say in New York City. The Internet site then displays a map at an intermediate level of detail and the user can click the “Zoom Out” or “Zoom In” button so as to display progressively larger geographical areas (with less detail) or progressively smaller geographical areas (with more detail, even to the level of individual streets and buildings). This technique has not previously been used to display different levels of anatomic detail in pain diagrams.
Since the late 1970s, workers in the field of comparative anatomy have used geometric morphometrics to compare the anatomic features of different groups of organisms. Geometric morphometric methods identify the location of selected anatomic landmarks and then apply techniques such as thin-plate spline transformation to warp an image by transforming input coordinates to output coordinates. Similarly, Gupta et al (U.S. Pat. No. 5,848,121) have described transformation of images in digital subtraction angiography using user-provided match points as the basis for interpolation techniques that correct mismatches between a mask and an opacified image. Such methods have not hitherto been applied to match pain diagrams of different designs.